Unless the try gun was identical to the guns you're having built the measurements will change. If you're comfortable with the old stock dimensions you'll run less risk using them than what some gun fitter cooked up.
Incidentally, two good independent gun fitters will almost always give you two very different measurements.
I would agree with your first point, though the dimensions should be close and will give a good idea if the OPs measurement session did produce good results.
I can't agree with the second point. Two good independent gun fitters
should produce 'similar' if not identical results. The reason is that the gun fitter is fitting the gun both to your physical dimensions, but also dynamic shooting style. If very different results are obtained from different fitters (one gun, one shooter), either the shooter is inconsistent, or one of the gun fitters is not up to the task.
I have been fitted twice (two different guns, two different both experienced and respected fitters) and the results were very close (within 1/8" in all cases). Bearing in mind this was for an o/u and a s/s, I regard this as consistent. The s/s also ties exactly with another s/s I was sold as 'fits you like a glove' by a very experienced and reputable dealer some years before (without a formal fitting).
I shoot well (for me anyway) with all of the guns - and they feel 'right'.
